Arsenic (As), our topic of interest today, is a chemical element found in many minerals. It usually occurs in trace quantities in all rocks, soil, water and air. As is currently classified as groundwater contaminant in many parts of South-East Asia including many parts of India. According to WHO guidelines, the permissible As level in drinking water is 0.01 mg/l (10 μg/l). WHO has recognized Asas a major health concern in these areas. The states in and around the Ganga-Brahmaputra Fluvial plains i.e. West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, Manipur and Chhattisgarh are considerably affected.

Figure 1 Map of India with the states in and around Ganga-Brahmaputra Fluvial plains indicated! The image was generated using viz.socialcops.com

Currently, WHO has warned that the long-term intake of As-contaminated groundwater causes Arsenicosis which can lead to cancer of skin, bladder, kidney and lung and disease. Arsenicosis also causes inhibition of essential enzymes, in extreme cases, resulting in multi-system organ failure and death. The common symptoms of Arsenicosis include skin discolourations and hard patches on palms and soles. In some cases, discolouration of blood vessels of legs and feet may also occur. Recent scientific evidence also suggests an association between the intake of As-contaminated water and onset of lifestyle diseases such as diabetes and hypertension. Reproductive disorders are also implicated.

Figure 2 Classical skin discoloration and hard patches on palms and soles with arsenicosis. The image is taken from the UNICEF report on countrywide arsenic poisoning in Bangladesh in the early 1990s.

The inorganic forms ofAs, As (III) and As (V), are highly toxic (As (III) being the most toxic) and lead to chronic toxicity. Methylated As are also highly toxic. Other than the natural sources that result in As leaching from sediments and soils, industrial processing, wood preservatives, acid mine drainage and burning of fossil fuels increase As levels in water. When smaller amounts of As are ingested, it is excreted through urine. However, larger amounts accumulate inside the human body and lead to adverse effects as discussed above.

Recent reports of As exposure in the Indian subcontinent

As discussed above, people living in and around the Ganga–Brahmaputra Fluvial plains are at risk of As poisoning. Proximity to Bangladesh, an already As-exposed country, should be noted. Reporting of cases of As poisoning are on the rise. In the reference section, you will find some news articles reporting new As–cases (as new as 2017). Due to the location, Bihar is the most affected state (see the news article).

What can we do?

Unfortunately, you can not remove As from drinking water by common methods. Boiling water actually concentrates As as it evaporates. Reverse osmosis (RO) is able to remove As from drinking water although the water may require pre-treatment if it is muddy. In affected regions, it may become crucial to remove As using RO filter technology to reduce the chronic on-going As exposure. As many of these parts come under ‘poor to very poor’ category, the water treatment should be done at the treatment plant as it may not be possible for poor people to remove As from water on their own.

While As is present in small quantities in the freshwater sources, it is unclear at this time as to what are the exact industrial sources which are responsible for increasing As levels to such harmful amounts. Well-organized studies will be needed to assess the sources and to restraint the activities.